A light module for displaying a signal in a rearview mirror is described in international patent application WO 2004/024502 A1. The light module, which is arranged on the back of the mirror glass of a rearview mirror of a motor vehicle, consists of a rigid circuit board that is fitted with LEDs on the side facing the back of the mirror glass. This publication puts forward cables in order to connect the circuit board to a current/voltage supply or to a control unit. The LEDs serve to display differently lit symbols in the surface of the mirror glass in order to indicate special driving or ambient situations of the vehicle such as, for example, an activated turn signal, an approaching vehicle in the blind spot, etc.
A drawback of the prior-art light module is that its structure is very complex and requires a great deal of installation space.